Flat display tube utilizing unique collimator



Feb. 23, 1965 D. GABOR 3,171,056

FLAT DISPLAY TUBE UTILIZING UNIQUE COLLIMATOR Filed May 15, 1965 3 Sheets-Sheet l DENN IS GABOR W W,

A TTORA/E Y6 Feb. 23, 1965 D. GABOR 3,171,056 FLAT DISPLAY TUBE UTILIZING UNIQUE COLLIMATOR Filed May 13, 1963 3 Sheets-Sheet 2 IN VEN TOR DENN 15 GABOR wwn,mmmn

A TTOR/VEYJ Feb. 23, 1965 FIGS.

D. GABOR 3,171,056

FLAT DISPLAY TUBE UTILIZING UNIQUE COLLIMATOR Filed May 13, 1965 3 Sheets-Sheet 3 DEN N 15 GABOR A TTOEWB K3 United States Patent Office 3,171,056 Patented Feb. 23, 1965 3,171,056 FLAT DISPLAY TUBE UTILIZING UNIQUE COLLIMATOR Dennis Gabor, London, England, assignor to National Research Development Corporation, London, England, a British corporation Filed May 13, 1963, Ser. No. 279,758 Claims priority, application Great Britain, May 15, 1962,

2 Claims. (Cl. 315-18) This invention relates to cathode ray tubes and more particularly to tubes primarily suitable for television.

The invention has particular application in tubes which have relatively small depth in the direction normal to the screen and which may be termed flat cathode ray tubes. Such tubes are described in US. patent specification No. 2,795,729 which discloses tubes of the kind in which an electron beam is provided in a plane parallel to a fluorescent screen and which have an electrode array in a plane parallel to, but spaced apart from, the screen which is arranged to set up an electrostatic field having a component normal to the screen which serves to deflect an end portion of the beam towards and into impact with the screen. This field also provides the frameor Y-scan. Prior to coming under the influence of this electrostatic field it is necessary for the beam to be deflected in the line or X direction and it is often desirable for the deflected beam to be collimated, that is for the deflected beam to be aligned in a direction parallel to a central axis but spaced therefrom by a distance dependent on the amount of the original deflection.

. In US. patent specification No. 2,872,607 there is deprising two similar composite plates positioned parallel to each other and between which the deflected beam is arranged to pass, said plates each comprising a plurality of conductive areas or islands positioned symmetrically on both sides of a central axis which are insulated from each other and which are shaped so that when appropriate different potentials are applied to said areas or islands which progressively decrease away from the axis a collimating electric field is produced which bends an electron beam by an amount which is greater for greater initial deflection of the beam away from said axis so as to align said beam parallel to said axis.

The means for deflecting the electron beam in a single plane may comprise a pair of deflection and positioned on opposite sides of the electron beam and diverging progressively apart along the beam and a pair of gen erally fan-shaped conducting plates spaced apart generally perpendicularly to the plane of deflection on opposite sides of the beam which together with the deflection plates define a flared-out volume within which the beam can be deflected and in which in operation the deflection plates are arranged to have differential changes in potential applied thereto and the fan-shaped plates are held at a potential intermediate to the deflecting plates.

The invention has important application in flat cathode ray tubes of the kind in which the electron beam is turned through 180 by means of a reversing lens before impingement on the screen, in which case it is preferable for the deflector and collimator to be positioned in the path of the beam before the reversing lens. However, the invention is not limited to such an arrangement and is equally applicable to arrangements which do not incorporate a reversing lens.

- In order that the invention may be more fully understood reference will now be made to the drawings accompanying this specification in which:

' FIG. 1 is a side-sectional view of a flat cathode ray tube embodying a deflector and collimator according to the invention;

FIG. 2 is a perspective view of the deflector shown in FIG. 1; and

FIG. 3 is a view of a combined deflector and collimator embodying the invention.

Referring now to FIG. 1 there is shown therein a cathode ray tube having an evacuated container 1 at least one wall 2 of which is transparent, conveniently being constructed of glass, and is provided with a fluorescent screen 3 on the inner surface thereof. An electron gun 4 is provided which generates an electron beam, indicated by the dotted line 10, in a direction parallel to the plane of screen 3. The path of the beam extends for substantially the entire height of the tube parallel to screen 3 and is then turned through by means of a reversing lens 5 held at substantially cathode potential and [is accelerated in a direction anti-parallel to its original direction by means of an anode 6. The beam now passes between the screen 3 and a scanning array 7 which is in spaced-apart parallel relationship to screen 3. The construction of scanning array 7 is described in detail in patent specification No. 2,795,729 and as described therein is arranged to set up an electrostatic field having a component normal to the screen which serves to deflect an end portion of the beam towards and into impact with the screen. This field determines the height along screen 3 at which impingement occurs and hence'controls the frameor Y-scan of the tube although other scanning means can be used if desired. The lineor X-scan of the tube is controlled by means of a deflector 8 and a collimator 9 illustrated diagrammatically in FIG. 1 and which will be described in greater detail below.

Deflector 8 is illustrated more clearly in FIG. 2 and comprises a pair of deflection plates'll and 12 spaced apart in the plane of deflection and positioned on opposite sides of the electron beam and diverging progressively apart along the beam. Plates 11 and 12 lie in planes perpendicular to the plane of deflection with the addition of small flanges 13 and 14 which extend parallel to the plane of deflection and are'provided-on the plates where they are closest together at the position where the beam first enters the deflector. Deflection of the beam is caused by applying differential changes of potential to the two plates 11 and 12. The deflector also includes additional planar fan-shaped plates 15 and 16 which are parallel to the plane of deflection and are positioned on either side of the electron beam. Plates 15 and 16 are insulated from plates 11 and 12 but together these plates substantially enclose a flared-out volume within which deflection of the beam can occur. In operation the fan-shaped plates 15 and 16 are held at a fixed potential which is the mean of the potentials applied to plates 11 and 12, for instance by connection to the mid-joint of a potential divider chain connected between plates 11 and 12.

Alternatively, it can be arranged that the fan-shaped plates 15 and 16 are always at the potential of the more negative of the two deflection plates 11 and 12. This can be achieved by connecting plates 11 and 12 to the plates 15 and 16 through individual rectifiers in such a way that current flows from plates 15 and 16 to which- 3 ever of plates 11 and 12 is the more negative at any instant.

The eflect of plates 15 and 16 is to improve the deflection sensitivity since marginal beams will travel all the way in a strong electric field. They also reduce the deflection focusing because the field intensity has a gradient outwards so that the outer portion of a beam is deflected more than the inner portion of the beam, which is opposite to the case in deflectors hitherto. A convenient operating potential for the deflector, that is the potential which is applied to plates 15 and 16 and the mean of the potentials applied to plates 11 and 12 is about one quarter of the voltage V that is applied to the final anode 6.

Even more convenient operation can be obtained by dividing the plates 15 and 16 into wedged-shaped segments and applying to these a potential distribution with a chain of resistors joining these in series with one another and to the two deflectors 11 and 12, such that while the potential of the middle segment remains at the mean potential of the two deflector plates, the potential increases towards the outside segments to about two-thirds of the potentials of the said deflector plates. The number of the segments is conveniently taken to be seven.

The beam on leaving the deflector diverges angularly by an amount dependent on the degree of deflection and traverses the collimator 9, illustrated in detail in FIG. 3, which serves to ensure that the electron beam approaches the reversing lens 5 in a direction which is always parallel to the original direction of the beam emitted from electron gun 4 irrespective of the amount of deflection. The resultant effect of deflecting the beam is thus to displace the beam laterally from its original direction but not to change its angular orientation. The collimator is therefore required to bend the deflected beam by an amount which is dependent on the magnitude of the original deflection.

The collimator comprises two parallel composite plates such as plate 17 between which the deflected electron beam is passed in directions parallel to the plane of the plates. The plates themselves are identical in shape with each other and are each symmetrical about a central axis XX in FIG. 3 which is concurrent with the original direction of the electron beam. The plates themselves comprise a plurality of conductive areas or islands 18 insulated from each other and connected to a potential divider chain (not shown) so that the potentials of the islands progressively decrease away from the central axis XX. Suitable potentials for applying to the islands are marked in the figure as proportions of anode voltage V. Typical trajectories of an electron beam are illustrated by the dotted lines 19. Printed circuit techniques can be conveniently used to form the islands.

FIG. 3 also illustrates the manner in which the deflector illustrated in FIG. 2 can be combined with the collimator in a single structure. The two deflection plates 11 and 12 are illustrated in section while the fan-shaped plates 15 and 16 constitute the first of the islands of the collimator.

The islands are shaped so as to produce electric fields which bend the electron beam by the requisite amount to align any beam leaving the deflector into a direction parallel to the axis XX and also focus any beam once and once only in the vertical direction in the figure. FIG. 3 is a scale drawing of a suitable collimator, but if desired the number of islands and the potential grading can be modified provided the general pattern shown in the figure is maintained.

I claim:

1. A cathode ray tube including an electron beam source, means for deflecting the electron beam from said source in a single plane, together with a collimator for aligning a deflected beam along lines in said plane parallel to each other, said collimator comprising two similar composite plates positioned parallel to each other and between which the deflected beam is arranged to pass, said plates each comprising a plurality of mutually insulated conductive areas or islands positioned symmetrically on both sides of a central axis and which are so shaped that when appropriate diflerent potentials are applied to said areas or islands which progressively decrease away from the axis a collimating electric field is produced which bends an electron beam by an amount which is greater for greater initial deflection of the beam away from said axis so as to align said beam parallel to said axis.

2. A cathode ray tube including an electron beam source, a deflector for deflecting the electron beam from said source in a single plane comprising a pair of deflection plate spaced apart in the plane of deflection and positioned on opposite sides of the electron beam and diverging progressively apart in the direction of the electrons and a pair of generally fan-shaped conducting plates spaced apart generally perpendicularly to the plane of deflection one on each side of the beam which together with the deflection plates define a flared-out volume within which the beam can be deflected said deflection plates being insulated from said fan-shaped plates together with a collimator for aligning a deflected beam along lines in said plane parallel to each other, said collimator comprising two similar composite plates positioned parallel to each other and between which the deflected beam is arranged to pass, said plates each comprising a plurality of mutually insulated conductive areas or islands positioned symmetrically on both sides of a central axis and in the same plate as said fan-shaped plates and which are so shaped that when appropriate different potentials are applied to said areas or islands which progressively decrease away from the axis a collimating electric field is produced which bends an electron beam by an amount which is greater for greater initial deflection of the beam away from said axis so as to align said beam parallel to said axis.

References Cited by the Examiner UNITED STATES PATENTS 2,926,274 2/60 Gabor 313-77 DAVID G. REDINBAUGH, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 5,171 ,056 February 25, 1965 Dennis Gabor It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 56, after "deflection" insert plates spaced apart in the plane of deflection column 4, line 46, for "plate" read plane Signed and sealed this 27th day of July 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,171,056 February 23, 1965 Dennis Gabor error appears in the above numbered pat- It is hereby certified that t the said Letters Patent should read as ent requiring correction and the, corrected below.

"deflection" insert plates Column 1, line 56, after column 4, line 46,

spaced apart in the plane of deflection for "plate' read plane Signed and sealed this 27th day of July 1965.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER Attesting Officer 

1. A CATHODE RAY TUBE INCLUDING AN ELECTRON BEAM SOURCE, MEANS FOR DEFLECTING THE ELECTRON BEAM FROM SAID SOURCE IN A SINGLE PLANE, TOGETHER WITH A COLLIMATOR FOR ALIGNING A DEFLECTED BEAM ALONG LINES IN SAID PLANE PARALLEL TO EACH OTHER, SAID COLLIMATOR COMPRISING TWO SIMILAR COMPOSITE PLATES POSITIONED PARALLEL TO EACH OTHER AND BETWEEN WHICH THE DEFLECTED BEAM IS ARRANGED TO PASS, SAID PLATES EACH COMPRSING A PLURALITY OF MUTUALLY INSULATED CONDUCTIVE AREAS OR "ISLANDS" POSITIONED SYMMETRICALLY ON BOTH SIDES OF A CENTRAL AXIS AND WHICH ARE SO SHAPED THAT WHEN APPROPRIATE DIFFERENT POTENTIALS ARE APPLIED TO SAID AREAS OR "ISLANDS" WHICH PROGRESSIVELY DECREASE AWAY FROM THE AXIS A COLLIMATING ELECTRIC FIELD IS PRODUCED WHICH BENDS AN ELECTRON BEAM BY AN AMOUNT WHICH IS GREATER FOR GREATER INITIAL DEFLECTION OF THE BEAM AWAY 